I got Critic badge yesterday, but My user page > Activity > votes > downvote say "you have not cast any votes". It seems strange, so I report it. I have something likely come to mind. After I voted up for someone's question (maybe from 1 to 2 votes), I wondered I'd voted him before and did vote-down to cancel it. But I surprised because of two down by one click and I hastily did vote-up again (0 to 2). This is all I remember. Is this a bug ?
I found this is the reproducible problem. In this meta community, I've done vote-up and subsequently tried to do vote-down. The System prevented me from doing vote-down (i.e., I failed to do vote-down), but I got Critic badge.